For decades, motorists zooming over the Dumbarton Bridge have had a fairly stark view as they approached Menlo Park: a muddy industrial salt pond, streaked with white saline markings and devoid of much life.

That landscape is about to change, with the completion of the latest wetlands restoration project in the ongoing renaissance of San Francisco Bay and its shoreline.

“There should be thousands, if not tens of thousands, of birds here in the next few months. Just add water and they come,” said Mendel Stewart, manager of the Don Edwards San Francisco Bay NationalWildlife Refuge.

For more than a year, construction crews with heavy machinery working for the U.S. Fish and Wildlife Service have been turning the former Cargill Salt pond here into a rich environment for dozens of bird species.

The finished project will officially open this morning at a ceremony attended by Sen. Dianne Feinstein, D-Calif., and state Resources Secretary Lester Snow.

At the site, once known as Pond SF2, where salt was produced through evaporation for roads, food and medicine, workers have converted 237 acres into a network of 30 islands, each about half an acre, for avocets, sandpipers, plovers and other shorebirds to nest. They have built public trails, elevated overlooks and interpretive exhibits. The project, located on the southern edge of Dumbarton Bridge adjacent to a former skeet shooting club that closed in 1994, is part of the restoration of a vast network of former Cargill ponds that make up 20 miles of the South Bay shoreline from Hayward to San Jose to Redwood City.

In 2003, the federal and state governments spent $100 million to buy 16,500 acres from Cargill Salt, based in Newark. The goal: to turn back the clock a century and reestablish healthy marshes for ducks, shorebirds, fish and other wildlife — launching the largest wetlands restoration on theWest Coast.

After five years of public meetings and environmental reviews, construction is under way in earnest.

By the end of this year, 3,081 acres in the South Bay and 1,400 acres in the North Bay near Napa will have been restored to tidal marsh or be under construction. That total of nearly 4,500 acres represents more than a quarter of the entire, massive Cargill transformation. An additional 600 acres off Alviso and Hayward are set to be restored back to tidal marsh by 2012.

“I fly over the Bay all the time,” said Feinstein, who oversaw the Cargill deal. “Instead of these bright orange patches, what you are beginning to see now is Bay water and some wetlands growth. For me, it’s very exciting.”

Abig challenge, however, is cost, she said.

Restoration of Pond SF2 cost $9.2 million, paid for with $7.6 million in federal funds and $1.6 million from Caltrans and Menlo Park.

The high price tag, according to the U.S. Fish and Wildlife Service, is because of the unique restoration work. The 50-year plan for restoration of the Bay calls for converting as much as 90 percent of all the former salt ponds to tidal marsh. In those areas, crews with bulldozers are often able to simply breach earthen levees, strengthen inner levees to provide flood protection, and wait for plants and wildlife to come back in a few years. Those ponds can cost as little as $1 million each to bring back to pre-Gold Rush conditions.

But Pond SF2 is different.

It is designed as a unique “managed pond” where the water will remain 12 inches deep, and the tides will be carefully controlled to provide habitat for shorebirds. If the water gets too shallow, it will stagnate. If it gets too deep, birds can’t wade there. Restoration requires a complex system of weirs, berms and culverts, and 11 huge steel tidal gates.

“There’s nothing else like it anywhere in the Bay,” said John Bourgeois, manager of the South Bay Salt Restoration Project.

State and federal officials estimated three years ago that the whole Cargill restoration would cost $987 million over the next 50 years, most of it to upgrade flood-control levees around South Bay communities.

In April, U.S. Rep. Jackie Speier, D-San Mateo, introduced a bill to provide $100 million a year for 10 years in federal funding to cover the costs. But Feinstein, who heads the Senate Appropriations Subcommittee on Interior and Environment, said that’s not politically feasible.

“That’s not going to happen. Trust me, it’s impossible,” she said on Friday.

Private foundations, state bond funds and individual donors will have to pay a large amount of the cost, she said.

David Lewis, executive director of Save the Bay, an environmental group in Oakland, said $1 billion over 50 years is the same or less as restoration projects have been given in the Everglades, Great Lakes and other nationally important sites.

Lewis, whose group is seeking volunteers to plant thousands of native plants at Pond SF2, is also part of a group studying the feasibility of putting a sales tax or small property tax, perhaps $5 a year, before Bay Area voters to fund Bay restoration.

“It’s a bargain,” he said. “You get habitat for wildlife, recreation, water quality and flood protection. San Francisco Bay is one of the rarest and most precious habitats on earth.”